作者机构：
[Tian Da-Lun; Wang Guang-Jun; Fang, Xi; Yan Wen-De; Kang Wen-Xing] Cent S Univ Forestry & Technol, Fac Life Sci, Forest Ecol Sect, Changsha 410006, Hunan, Peoples R China.;[Chen Xiao-Yong] Governors State Univ, Coll Arts & Sci, Biol Program, University Pk, IL USA.
通讯机构：
[Yan Wen-De] C;Cent S Univ Forestry & Technol, Fac Life Sci, Forest Ecol Sect, Changsha 410006, Hunan, Peoples R China.
关键词：
fine roots;forest management;soil carbon;soil moisture;soil temperature
摘要：
Soils play a critical role in the global carbon cycle, and can be major source or sink of CO_2 depending upon land use, vegetation type and soil management practices. Fine roots are important component of a forest ecosystem in terms of water and nutrient uptake. In this study the effects of thinning and litter fall removal on fine root production and soil organic carbon content were examined in 20-year-old Masson pine (Pinus resinosa) plantations in Huitong, Hunan Province of China in the growing seasons of 2004 and 2005. The results showed that fine root production was significantly lower in the thinning plots than in the control plots, with a decrease of 58% and 14% in 2004 and 2005 growing seasons, respectively. Litter fall removal significantly increased fine root production by 14% in 2004. Soil temperature (T_(soil)) and soil moisture (M_(soil)) were higher in the thinning plots than those in the controls. Litter fall removal had significant effects on T_(soil) and M_(soil). Soil organic carbon content was higher in the thinning plots but was lower in the plots with litter fall removal compared with that in the controls. Our results also indicated that annual production of fine roots resulted in small carbon accumulation in the upper layers of the soil, and removal of tree by thinning resulted in a significant increase of carbon storage in Masson pine plantations.
作者机构：
[Wang GuangJun; Yan WenDe; Xiang WenHua; Tian DaLun; Peng ChangHui] Cent S Univ Forestry & Technol, Fac Life Sci & Technol, Changsha 410004, Hunan, Peoples R China.;[Peng ChangHui] Univ Quebec, Dept Sci Biol, Inst Environm Sci, Montreal, PQ H3C 3P8, Canada.
通讯机构：
[Tian DaLun] C;Cent S Univ Forestry & Technol, Fac Life Sci & Technol, Changsha 410004, Hunan, Peoples R China.
关键词：
carbon cycle;soil CO2 flux;soil moisture;soil temperature;temporal dynamics
摘要：
Climate change can significantly affect carbon cycling of forest ecosystems. The diurnal and seasonal dynamics of soil respiration (R
s) in Cinnamomum camphora and Liquidambar formosana forests were investigated by using infrared gas exchange analyzer of Li-Cor 6400-09 each month in 2006. Soil temperature and moisture were also measured. Diurnal variations in R
s varied with daily soil temperature in the two forests. Across the growing season, soil respiration peaked on July 28 due to higher soil temperature and moisture conditions. Seasonal R
s variations were predominantly influenced by soil temperature. Seasonal soil respirations in C. camphora and L. formosana forests were strongly related to soil temperature (x) at 5-cm depth (R
s = 0.1598e0.1377x
(R
2 = 0.9289, P = 0.001) and R
s = 0.2177e0.0962x
(R
2 = 0.927, P = 0.000)), while annual mean R
s rate was 2.614 and 1.397 μmol m−2 s−1 and Q
10 values was 3.96 and 2.62 for the two forests, respectively. However, R
s was not influenced by seasonal changes in soil moisture (w) in the two forests in 2006. We developed two equations (R
s = −0.020w
2+0.497w+0.562 (R
2 = 0.109, P > 0.05), R
s = −0.001w
2+0.072w+0.731(R
2 = 0.053, P > 0.05)) to describe the relationship between R
s and soil moisture. A positive relationship between R
s and soil moisture were observed when soil moisture was below 12.43% and 18.00%, but when soil moisture exceeded threshold values of 12.43% and 18.00%, soil moisture became the restraint factor for R
s. Long-term observations of soil respiration and moisture are required to understand the temporal dynamics of soil respiration.
作者机构：
[Tian Da-Lun; Yan Wen-De; Fang Xi; Kang Wen-Xing; Deng Xiang-Wen; Wang Guang-Jun] Cent S Univ Forestry & Technol, Fac Life Sci & Technol, Forest Ecol Sect, Changsha 410006, Hunan, Peoples R China.
通讯机构：
[Tian, DL ] ;Cent S Univ Forestry & Technol, Fac Life Sci & Technol, Forest Ecol Sect, Changsha 410006, Hunan, Peoples R China.
关键词：
forest;soil moisture;soil properties;soil respiration;soil temperature
摘要：
Forest management is expected to influence soil CO2 efflux (FCO2) as a result of changes in microenvironmental conditions, soil microclimate, and root dynamics. Soil FCO2 rate was measured during the growing season of 2006 in both thinning and non-thinning locations within stands ranging from 0 to 8 years after the most recent thinning in Chinese fir (Cunninghamia lanceolata (Lamb.) Hook) plantations in Huitong Ecosystem Research Station, Hunan, China. Soil temperature and moisture were also measured to examine relationships between FCO2 and soil properties. Forest thinning resulted in huge changes in FCO2 that varied with time since cutting. Immediately following harvest (year 0) FCO2 in thinning area increased by about 30%, declined to 20%–27% below pre-cutting levels during years 4–6, and recovered to pre-cutting levels at 8 years post-cutting. A similar temporal pattern, but with smaller changes, was found in non-thinning locations. The initial increase in FCO2 could be attributed to a combination of root decay, soil disturbance, and increased soil temperature in gaps, while the subsequent decrease and recovery to the death and gradual regrowth of active roots. Strong effects of soil temperature and soil water content on FCO2 were found. Forest thinning mainly influenced FCO2 through changes in tree root respiration, and the net result was a decrease in integrated FCO2 flux through the entire felling cycle.
摘要：
在土壤-植物-大气连续体构成的水流路径中,树干液流量制约着整个树冠的蒸腾量,如何直观、精确和连续测定水分在木质部中的流动速率是科学家们一直在探索和渴望解决的问题(Baker et al.,1987).近几十年来,国内外相关领域的学者们相继提出了一些诸如称重法、截干法和茎流速率法等不同的测定方法,目前茎流速率法应用最为广泛.茎流速率法主要包括放射法同位素示踪法、染色法、热脉冲法、热扩散探针法、热平衡法和核磁共振图像扫描法,这些方法在使用上都有一定的适用性和局限性(刘奉觉等,1997).
